Summer might be over, but the sun still shines on one Greater Washington company.

Monday Properties announced this week the successful renewal of a 53,000-square-foot lease at 1515 Wilson Blvd., a deal that keeps the building’s anchor and its more than 200 employees from leaving and maintains a 90 percent occupancy rate for the property.

Tetra Tech AMT, an industry-leading IT and aerospace management service provider to government and private-sector commercial customers, has been calling 1515 Wilson home for almost 18 years now. As part of the renewal agreement, it will occupy the top five floors of the building. This means the company will relocate some of its employees, currently on the third floor, to the newly constructed eighth floor. In addition, Monday Properties has agreed to provide Tetra with new rooftop signage.

Monday Properties was represented in house by Tim Helmig, John Wharton and Deniz Yener in the lease transaction. Tetra was represented by Cathy Delcoco and Brad Davis of CBRE Group Inc.

“As with many of our tenants, we’ve been a long-term partner with Tetra Tech AMT and have worked to accommodate their growth for nearly two decades,” Helmig, president & COO of Monday Properties, said in a statement. “Tetra Tech AMT’s renewal continues the positive response to the extensive renovations and new on-site restaurant options at 1501 and 1515 Wilson, with the top floors of both buildings leasing in the last four months. We are very encouraged by the recent leasing and retail activity in Rosslyn, which has now clearly transitioned into a preferred location for attracting and retaining a highly educated workforce.”

Monday Properties has invested more than $5 million in recent years to improve the two office buildings at 1515 and 1501 Wilson Blvd. Renovations have included a new lobby, new elevators and HVAC systems, improved public areas, a fitness facility and a large outdoor-activity plaza.

Tetra’s renewal is just the latest in a long line of successful deals for Monday Properties at 1515 and 1501 Wilson Blvd. ICA Language Services signed a lease for 17,000 square feet of space at 1501 Wilson in April, while SeKON and Serka Federal Solutions have taken approximately 6,000 square feet in the same building.